import { inspectLock, isLockGuardHeld, isStaleLock, type LockInspection } from "./lock.js";
import { errorMessage } from "./manager-helpers.js";
import type { LockFile } from "./types.js";

export type OperationAvailability =
	| { kind: "free" }
	| { kind: "live"; lock: LockFile }
	| { kind: "busy"; lock?: LockFile; metadata: LockInspection["status"] }
	| { kind: "recoverable-stale"; lock: LockFile }
	| { kind: "recoverable-unreadable" }
	| { kind: "inspection-error"; message: string };

interface OperationInspectionDependencies {
	inspectMetadata(): Promise<LockInspection>;
	inspectGuard(): Promise<boolean>;
}

const DEFAULT_INSPECTION_DEPENDENCIES: OperationInspectionDependencies = {
	inspectMetadata: inspectLock,
	inspectGuard: isLockGuardHeld,
};

export async function inspectOperationAvailability(
	dependencies: OperationInspectionDependencies = DEFAULT_INSPECTION_DEPENDENCIES,
): Promise<OperationAvailability> {
	try {
		const metadata = await dependencies.inspectMetadata();
		const guardHeld = await dependencies.inspectGuard();
		return classifyOperationAvailability(metadata, guardHeld);
	} catch (error) {
		return { kind: "inspection-error", message: errorMessage(error) };
	}
}

export function classifyOperationAvailability(
	metadata: LockInspection,
	guardHeld: boolean,
): OperationAvailability {
	if (metadata.status === "valid" && !isStaleLock(metadata.lock)) {
		return { kind: "live", lock: metadata.lock };
	}
	if (guardHeld) {
		return {
			kind: "busy",
			metadata: metadata.status,
			...(metadata.status === "valid" ? { lock: metadata.lock } : {}),
		};
	}
	if (metadata.status === "valid") {
		return { kind: "recoverable-stale", lock: metadata.lock };
	}
	if (metadata.status === "unreadable") return { kind: "recoverable-unreadable" };
	return { kind: "free" };
}

export function operationBlocksChanges(availability: OperationAvailability) {
	return availability.kind !== "free";
}

export function operationCanRecover(availability: OperationAvailability) {
	return (
		availability.kind === "recoverable-stale" || availability.kind === "recoverable-unreadable"
	);
}